1. Field of the Invention
The present invention relates generally to apparatus for the storage and transport of heat-producing material, and, more particularly, to a cask basket construction for storage and transport of radioactive material.
2. Description of the Prior Art
Commercial nuclear facilities generate useful amounts of electrical power by creating heat energy which is converted into electrical power. The heat energy is generated as a by-product of a nuclear fission process which is permitted to occur at a controlled rate. In a commercial nuclear reactor power facility, a nuclear fuel source is positioned in a reactor core area of the facility whereat the controlled nuclear fission process occurs. Coolant water circulates in the reactor core in a heat transfer relationship with the nuclear fuel source, and the heat energy transferred to the coolant water is utilized to heat a secondary water system which, in turn, operates steam generators which produce electrical power.
The nuclear fuel source which fuels the fission process is supported in a supportive structure referred to as a nuclear fuel assembly.
A nuclear fuel assembly is comprised of a plurality of nuclear fuel rods which are hollow metal pipes filled with the nuclear fuel supported by a supportive structure such that the fuel rods are maintained in precisely spaced arrays. In this manner, the nuclear fission process can be controlled and moderated while most efficiently allowing coolant water to circulate in a heat transfer relationship with the fuel rods. Most commercial nuclear power facilities require more than one hundred fuel assemblies to be positioned in the reactor core in order to generate commercially useful amounts of heat to be converted into electrical power.
Over time, the heat generative properties of the nuclear fuel contained in the fuel rods of the fuel assemblies are reduced to an extent necessitating replacement of the "spent" fuel material. During such occasions, the entire fuel assemblies are removed from the reactor core and are replaced with fuel assemblies having fuel rods containing fresh nuclear fuel material. However, the fuel assemblies removed from the reactor core still contain residual amounts of nuclear fuel material which still posses significant heat generative properties.
In order to prevent overheating of the spent fuel assemblies after their removal from the reactor core, the spent nuclear fuel assemblies are immersed in water in storage areas referred to as spent fuel pits. The heat generated by the spent fuel assemblies is dissipated by the water circulating through the spent fuel pit.
As ever-increasing numbers of spent fuel assemblies have been placed in the spent fuel pits, space remaining for the storage of additional spent fuel assemblies has decreased. Because of this limited storage capacity, locations whereat the spent fuel assemblies can be stored for extended periods of time are needed. These long-term storage locations are selected for reasons other than their proximity to the commercial nuclear facilities. Means for transporting the spent fuel assemblies from their storage locations in the spent fuel pits to the locations allowing long-term temporary storage of the spent fuel is required.
When transferring the spent fuel from the spent fuel pits to the remote locations, care must be exercised in order to prevent a temperature rise of the spent nuclear material. Therefore, the means utilized to transport the spent fuel assemblies to their long-term storage locations must provide efficient means for dissipating heat generated by the waste material.
Furthermore, since the cost of fuel (e.g. diesel), required to power freight transport vehicles, like all fossil fuels, continues to upwardly spiral, careful attention should be paid in the design of the cask basket construction so as to maintain the construction not only environmentally safe but also as light in weight as possible. By doing so, the following advantages can be achieved. First, if the weight of the "empty" cask basket construction, per se, is minimized, so too is its filled weight and, therefore, the gross weight of the transport vehicle when the cask basket is loaded thereupon. Hence, less fuel would be expended by the transport vehicle per trip thereof. And second, for a fixed maximum permissible transport weight for either the filled cask basket construction or the transport vehicle, a "minimized" weight cask basket permits the quantity of the nuclear fuel which can be transported to be maximized whereby less trips may be required of the transport vehicle to transport the fuel. Third, minimizing the weight of the cask basket construction serves to render the construction more easily and, generally, more safely handleable.
It is accordingly an object of the present invention to provide a construction for storing radioactive material to allow transport of the nuclear material.
It is a further object of the present invention to provide a cask basket construction which includes a means for transferring heat generated by radioactive material stored in the cask basket construction to prevent overheating of the or the basket material.
It is yet a further object of the present invention to provide a lightweight yet high-strength and environmentally safe spent nuclear fuel cask basket construction.
Still other objects and advantages of the present invention will become apparent in light of the attached drawings and the written description of the invention presented herebelow.